The 21st Annual San Antonio Breast Cancer Symposium will be held at the San Antonio Marriott Rivercenter from December 8-11, 1999. It is an international meeting featuring state-of-the-art lectures by invited speakers and proffered papers on the experimental biology, etiology, prevention, diagnosis and therapy of breast cancer. Over 50 percent of the symposium participants are MDs and MD PhDs, and the majority of these are medical oncologists, followed by surgical, gynecologic, and radiation oncologists. The objective of the Breast Cancer Symposium is to provide a forum for discussion of basic and clinical research by participants from all over the world. It is accomplished by bringing top speakers of international renown to address current issues and trends and by providing an environment that encourages interaction and stimulation. Abstracts accepted for presentation are published in the journal Breast Cancer Research and Treatment. All symposia to date have been granted Category 1, AMA credit for continuing education.